My main thoughts on the new regeneration (I'm sure I'll have more come my podcast tonight):
1. I'm very glad they chose an actor who's worked with Chibnall in the past. Chibnall is brand new to this role and the main reason I was iffy about casting a woman as the Doctor is that he was liable to make a lot of missteps in his first season, doubly so if trying out a new dynamic, and the actress was likely to be blamed by fans for all of them (see: Colin Baker). I think that this will cut out a lot of that "new dynamic" portion because Chibnall will know a lot more about what's already funny or serious about Whittaker.
2. I can understand that some people may be iffy about this (again, it's a new dynamic the show's not used to). I refuse to understand people who claim that this is the end of the show, or this is enough reason to never watch again, or any other dramatic statement that absolutely reeks of "we don't like women in these here parts".
3. This makes me happy Bill is gone. It's not that I hate Bill, it's that we've had a lot of companions having a crush on the Doctor and I don't want the first female incarnation's first companion to be that. It doesn't mean I'll get my wish, but it's a step. I would actually applaud if the next companion was a gay man, and I really don't care how many people tuned out as a result.